In operating a modern surgical lamp, a light source in the surgical lamp is used to illuminate a work field, e.g., a surgical site. The area illuminated by the surgical lamp is typically called a light field. During a surgical procedure, a surgeon may adjust a pattern size of the light field for optimal viewing of the surgical site. As the pattern size of the light field is adjusted, it is beneficial to simultaneously adjust the light output of the surgical lamp. If the pattern size of the light field is reduced while the light output remains constant, the intensity of the light in the light field would increase. It is thus beneficial to simultaneously reduce the light output of the surgical lamp as the pattern size of the light field is reduced so that the intensity of the light in the light field remains substantially constant. In a similar fashion, as the pattern size of the light field is enlarged, it is beneficial to simultaneously increase the light output of the surgical lamp so that the intensity of the light in the light field remains substantially constant. In general, it is beneficial to maintain the intensity of the light in the light field substantially constant as the pattern size of the light field is changed during use.
The present invention provides a surgical lamp for controlling the light output of the surgical lamp both independently of, and simultaneously with, a change in a pattern size of the light field, to maintain a desired light intensity in the light field.